Netfabb - Innovative software solutions for 3D printing and additive manufacturing.
A360 VIEWER - Free online CAD Viewer
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
STP Viewer - Free STP Viewer - free software that lets you view 3D STEP files (.stp, .step file format).
meshmixer - meshmixer is an experimental 3D modeling tool for making 3D mashups without too much hassle.
Glovius - Extensible & customizable 3D viewer, for consumption of product design data.